A comparison of C3R3P3 and C6R3H3 as ligands using photoelectron spectroscopy and density functional theory

Photoelectron spectra have been recorded for [M(CO)(3)(eta(6)-(C3Bu3P3)-P-t)] (M = Cr, Mo or W) and [Mo(CO)(3)(eta(6)-(C3Bu3H3)-H-t)]. They are assigned by comparison with analogous spectra and density functional calculations. The phospha-arene complexes show a higher first IE than carbocyclic analogues. Electronic structure analysis indicates stronger bonding in the former as a result of greater metal-ligand back donation to the lower lying LUMOs of the P substituted ring.